Automatic dishwashing is a demanding field. Specialized detergent formulations are required to deliver efficient and effective sanitization and cleansing of dishware. The cleaning task includes both stain removal and tough food cleaning. Automatic dishwashing has some unique constraints as compared to fabric laundering. Spotlessness and lack of film on glasses and silverware is particularly important. In many laundering operations, in contrast, there is a tolerance for deposition, onto the substrate being cleaned, of substances which may be greasy, oily, soapy or lubricious. Such substances are often fabric softeners or fatty acid salts.
Automatic dishwashing or "machine dishwashing" as it is sometimes called also has significant differences as compared with hand dishwashing. In the latter operation, typical product formulations rely mainly on high-foaming detersive surfactants. Many such products use high-foaming quaternary ammonium surfactants. The consumer finds foam or lather to be very desirable in hand-dishwashing.
In modern automatic dishwashing formulations, tough food cleaning performance is essential. This is commonly accomplished by detersive enzymes. Alkalis are also used, but may be highly corrosive, especially at high levels. Stain removal is especially sought after by the consumer. This includes removal of stains deposited by hot beverages such as tea, coffee or the like. Stain removal is commonly accomplished by a variety of bleaches.
Several aspects of automatic dishwashing detergent compositions are markedly different from laundry compositions. For example, special nonionic surfactant types are needed owing to the very low tolerance for foam production in domestic spray-arm dishwashers. Builder systems tend to include significantly different silicates from those commonly used in laundry compositions. On the other hand, automatic dishwashing detergents, laundry detergents and other detergents such as hard surface cleaners may have features in common--for example, bleaching forms of such detergents desirably comprise cost-effective bleach systems.
Owing to the enzyme-deactivating nature of some of the most chemically effective bleaches, especially hypochlorite bleaches, compromise detergent formulations have often been provided. This includes formulations in which a relatively mild and enzyme-compatible hydrogen peroxide source, such as sodium perborate, is combined with the enzymes; optionally with tetraacetylethylenediamine (TAED) as a bleach activator.
Various efforts have been made to improve the efficacy of bleach activators and hundreds of such activators have been described in the literature; however, at present, only TAED appears to be commercially available in an ADD. Reasons for the lack of commercially successful improvements may include an emphasis on laundry improvements not easily adaptable for automatic dishwashing. Bleach activators may, for example, yield unacceptably depositing, foam-forming or malodorous peracids, none of which are acceptable for automatic dishwashing, especially in a spray-action domestic dishwasher. Unfortunately, there has been little teaching in the art as to which of the now so numerous bleach activators would be problem-free in the unique automatic dishwashing context. Other possible explanations for the lack of success of new bleach activators in automatic dishwashing is that they may simply be too costly or mass-inefficient.
The disclosure of many bleach activators in the context of laundry formulations includes the suggestion that quaternary-substituted versions of such activators may be of a depositing nature and have desirable fabric conditioning properties. See, for example, U.S. Pat. No. 4,751,015 at col. 3, lines 22-27. In light of this teaching and in view of the conventionally recognized need to minimize deposition tendencies of ingredients in automatic dishwashing, the automatic dishwashing detergent formulator would be inclined to avoid such bleach activators. This patent as well as EP 408,131 are illustrative of disclosures of bleach activators which may include chemical groups which may be cationic and/or which may form peroxycarbonic acids when perhydrolyzed.
Another quaternary substituted bleach activator is disclosed in EP 120,591 A1 published Mar. 10, 1984. The bleach activator has the structure RC(O)L wherein RC(O) is a particular acyl moiety and L is a leaving-group. It is disclosed that a quaternary nitrogen group can be included in L. Another similar disclosure is found in U.S. Pat. No. 4,681,592: see col. 10, line 29.
Additionally, EP 427,224 A1 and U.S. Pat. No. 5,220,051 describe laundry detergent compositions comprising polycationic compounds of the formula: ##STR1## in which X is assertedly a "cation", Y is an alkylene, Z is a specific noncharged carbonyl-containing group and A is an anionic group. Based on the further illustrations in the disclosure, X is understood to be a cationic or quaternary nitrogen-containing moiety covalently incorporated into the structure. Moieties in the positions indicated by X appear to be the only quaternary nitrogen in these compounds.
Bleach activators have even been described which comprise a cationic moiety on each side of a perhydrolyzable acyl moiety. See, for example, U.S. Pat. No. 5,093,022, formula (I) at col. 1, line 50 with the substituent Y shown at col. 2, lines 40-45; and JP 02011545 A2 which describes the following bisquaternary compounds as textile bleaches and softeners: ##STR2## wherein R.sup.1 and R.sup.7 are C.sub.1 -C.sub.22 alkyl; R.sup.2, R.sup.3, R.sup.5 and R.sup.6 are C.sub.1 -C.sub.5 alkyl, hydroxyethyl or hydroxypropyl; R.sup.4 is C.sub.2 -C.sub.3 alkylene; n is from 1 to 5 and X is an anion.
Compounds of interest for hair cream rinse formulations, have a different kind of bisquaternary structure: ##STR3## wherein R is a saturated normal alkyl group of at least 11 carbon atoms and Ph is phenyl. These are described in U.S. Pat. No. 3,959,461. Similar compounds, such as the 1,3-bis-trimethylammonium isopropyl esters of octanoic and decanoic acids, have been incorporated into laundry detergents as bleach activators. See U.S. Pat. No. 5,399,746. Such compounds, it has now surprisingly been discovered, are less effective and have certain disadvantages when used for bleach activation in automatic dishwashing detergents when compared to the bleach activators of this invention.
Whatever the bleach activators hitherto described for fabric laundering, it is not immediately evident which to select in order to improve automatic dishwashing detergents. Moreover, whatever the disclosures of the art, there remains a need for improved bleaching detergents, especially for automatic dishwashing purposes; likewise, there is an ongoing need for new, improved bleach activators.
It is therefore an object herein to provide improved detergent compositions, especially automatic dishwashing detergents, comprising multiquaternary bleach activators, especially certain multiquaternary bleach activators having specific structures disclosed hereinafter, preferably combined with a conventional hydrogen peroxide source such as sodium perborate. The detergents preferably have compact nonphosphate granular form and desirably include water-soluble silicates, low-foaming nonionic detersive surfactants particularly adapted for automatic dishwashing use, detersive enzymes, and other automatic dishwashing compatible ingredients, all formulated to deliver uncompromised levels of cleaning and stain removal without undesirable deposition on dishware, e.g., as measured by spotting/filming; and without odor- or foaming-deficiencies. Other objects include the provision of improved bleach activators for detergents, especially those designed for automatic dishwashing.